It has been the practice in the prior art to mount a first stage pressure regulator directly on the neck of an associated air tank and to provide two or three fixed outlet ports on the regulator for coupling the regulator to the second stage regulator, a pressure gauge, and a buoyancy vest or jacket. As other instruments and devices which depend on air from the air tank are added to the medley of devices carried by the diver, "Y" and "T" connectors have been connected to the outlet ports of the first stage regulator to connect each of the outlet ports to more than one device. This has resulted in a large number of hoses being connected at approximately the same place on the regulator, making it difficult if not impossible to prevent the connecting hoses from becoming entangled with one another. Where additional outlet ports have been provided they have been located for convenience of manufacture rather than for convenience of use by the diver.
Another characteristic of most present day first stage pressure regulators is the fact that maintenance and repair of the valve mechanism has required considerable expertise in disassembly and reassembly of the mechanism. It would be desirable to provide a first stage regulator in which the entire pressure regulating mechanism could be easily removed and replaced when in need of repair.